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1. To be taking or under the influence (of drugs). They've got me on a load of antibiotics to fight off the infection. He acts so crazy that sometimes I wonder if he's on drugs!
2. To be performing or displayed, as on a stage, on television, or in a venue. That new play is on at the National Theater this evening. They're showing my favorite film on TV tonight! I hear there's a great new band on at the bar down the road.
3. To perform exceptionally well or impressively. The home team is really on tonight, it looks like they'll have an easy victory.
4. To be in support of, have interest in, or plan to participate in some activity or thing. Yeah, I'm on for having a few drinks later! Mary said she's on to go to a movie tonight.
5. To do something as planned or according to schedule. Are you still on to pick me up from the airport tomorrow? The meeting is on at five o'clock.
be on (one)
1. To be one's fault or responsibility. This whole mess is on the sales department, not us! Fine. But if this goes wrong, it's on you. The mix up is on me, OK? I'm sorry!
2. Of a drink, meal, performance, etc., to have the expenses covered by one, especially as a gift or benefit to someone else. A: "How much do I owe you for the tickets?" B: "Nothing, it's on me." No, no, the meal is on the house—the boss insists.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
1. Be taking medication or an illegal drug, as in Are you on some antibiotic? or He was definitely on narcotics when it happened. [1930s]
2. Be in favor of something or willing to participate, as in We're going dancing after the play-are you on? [Colloquial; late 1800s]
3. Be engaged in some action, especially on the stage, as in Hurry up, you're on in five minutes. [Late 1700s]
4. Perform extremely well, as in I can't return Dan's serve-he's really on today. [Slang; second half of 1900s]
5. Be scheduled, as in Is tonight's rally still on? [Colloquial; second half of 1990s]
6. be on one. Be at one's expense, either as a treat or the butt of a joke. For example, This round of drinks is on me, or He enjoys a good laugh, even when the joke's on him. [Colloquial; second half of 1800s]
7. not be on. Be unacceptable, not allowable, as in I can't believe you'd cancel; that's just not on. This usage is more common in Britain than America. [Colloquial; 1930s] For a synonym, see not done. Also see be on to.
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
1. To be in contact with the upper or outer surface of something: There are toys on the rug. Frost is on the windowpane. Your glasses are on the kitchen table.
2. To be engaged or functioning. Used mostly of machines: When the spotlights are on, it gets very hot. Is the car engine still on?
3. To be connected with or broadcast by some communication system: You have been on the computer for three hours. Come listen; my favorite radio show is on.
4. To be precise, in good form, or well executed: My dart throwing was definitely on, and that night I got four bull's-eyes. The remarks you made were right on, and everyone understood immediately.
5. To be dependent on or desirous of something: I am on medication to lower my cholesterol. They suspect that their child is on drugs.
6. be on about To talk excitedly about something, especially to others who are not interested or do not understand: They are always on about the prizes their children keep winning. I don't know what he is on about, but he is giving me a headache.
The American Heritage® Dictionary of Phrasal Verbs. Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.